Line scan technology is used in applications that image large objects, are high-resolution, are high-speed, need perfect images, or need real-time correction of pixels' responses. The camera has a single line of pixels and either the camera or object is moved perpendicular to that line of pixels to build up a two-dimensional image of the object.
Line scan imaging is usually used in short depth of field applications, such as a flat scanner, web inspection, etc., so that the line illumination design can have a short depth of field. Also, the alignment between the image sensor and the illumination is not an issue.
For long working distance application without folding optics, a lens/imager is built in the center of collimated line light. The alignment of the image sensor and the illumination is not an issue since lens and illumination have coaxial design.
Usually, the optical path from the imager to a target is a long distance, such as greater than 1000 millimeters, in order to cover a wide view with a long depth of field. If an imaging system's optical line and illumination line are co-axial, the illumination has to be located far away from the target. In order to cover the depth of field, usually a very high f-stop lens, such as F/12 and higher is required. Currently, there is no way to separate into two depths of fields (i.e. near field and far field) with one imaging camera where the F-stop of the lens is lower so that the imaging system is more illumination efficient.